1. Field of the Invention
The present invention relates to a motor driver system and its control method, which are capable of controlling a current angle of a motor such that the current angle does not increase more than necessary when the motor operates in a field weakening region.
2. Description of the Related Art
A synchronous reluctance motor has a simple construction and is economical compared with general induction motors and synchronous motor driving systems. In addition, a converter that applies electric power to the synchronous reluctance motor uses a small power device, so the synchronous reluctance motor is more economical and has high reliability.
When the synchronous reluctance motor operates in a field weakening region, a motor driving voltage is not sufficient, so the current applied to the motor is generally increased to maintain a static torque. In this case, however, the current angle of a command current applied to the motor is increased freely without set limits. As a result, the current angle of the command current applied to the motor is increased by more than necessary, causing a problem that ripples are generated in the command current and/or the motor controlling becomes unstable.